1. Field of the Invention
The present invention relates to devices for monitoring the level of electrolyte in rechargeable aqueous electric storage batteries. More particularly, the present invention relates to a device for providing a positive indication that the minimum acceptable level of electrolyte is present in a battery cell.
2. Background of the Invention
Rechargeable or secondary electric storage batteries often contain an aqueous electrolyte, such as a dilute sulfuric acid in lead acid systems. These batteries have multiple cells connected in series and are widely used in many applications such as electric vehicles.
During normal use, the water in the electrolyte solution is depleted by the electrolysis that accompanies the charging process and for other reasons such as charge inefficiencies. This water loss needs to be replaced before a low electrolyte level results in damage to the battery cells. Thus, such batteries are typically "topped off" or replenished with water before permanent damage to the battery components result.
A long recognized problem in the industry has been the determination of when to add additional water. The actual point of time when topping off is required is not easily determinable as battery utilization varies greatly with each application. Regular visual monitoring, such as looking into the battery cell, is typically required. Nevertheless, a main cause of battery failure is due to the lack of water. Furthermore, too frequent watering without proper visual monitoring can lead to overfilling and spilling of electrolyte.
Various devices are known in the art for monitoring electrolyte levels. Some of these units are deficient in that they are not fail safe. These units provide a positive indication, such as a light, only when the electrolyte liquid level falls below the minimum acceptable level. Such units are not capable of differentiating between a low electrolyte level and a failed monitor device. If no indication is given, it could mean that the electrolyte level is okay, or it could be that the unit has failed, in which case reliance on the monitor could result in a damaged battery.
More recently, supposedly fail safe monitors have been introduced. Such monitors are placed within the battery cell and positioned at a predetermined minimum acceptable electrolyte level to contact the electrolyte and give a positive indication when the electrolyte is just at the minimum acceptable level or higher. Such systems would have the advantage that a positive signal means that the liquid level is acceptable. If no indication were given, either the liquid level is low or the monitor is not working. In either event, the lack of a positive indication would mean that something is wrong and that further investigation is required.
These supposed fail safe devices, however, have in reality failed. It has been found that such devices can give a false signal indicating that the electrolyte level is acceptable when in fact the electrolyte is below the minimum acceptable level.
Accordingly, one object of the present invention is to provide a monitoring device which provides a positive indication when the electrolyte is at the minimum acceptable level.
Another object is to provide a monitor that is fail safe and not prone to false indications.
A further object of the present invention is to provide a simple and reliable monitoring device that has no moving parts to fail and that is virtually maintenance free.
Another object of the present invention is to provide a monitoring device that does not require a separate power source which can be depleted or fail.
Additional objects, advantages and novel features of the invention will be set forth in the description which follows, and in part should become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.